Display and method for repairing defects thereof

ABSTRACT

It is an object of the invention to provide a display and a method for repairing defects of the same in which defects such as inter-layer short-circuits and short-circuits in a single that have occurred at steps for manufacturing the display can be easily repaired to provide a good product with a probability higher than that in the related art. Laser irradiation is carried out as a first cycle of laser irradiation by forming a slit S 1  in a region where a drain bus line  220  completely covers a gate bus line  218  to form a cut portion longer than the width of the gate bus line  218  adjacent to an inter-layer short-circuit  290  such that it splits an intersecting portion of the drain bus line  220  into two parts as shown in FIG.  5   b.  Next, as shown in FIG.  5   c,  slits S 2  and S 3  are respectively used for second and third cycles of laser irradiation to cut the drain bus line  220  at both ends of the cut portion (indicated by S 1 ), thereby isolating the inter-layer short-circuit  290  of the drain bus line  220.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display and a method for repairingdefects thereof and, more particularly, to a liquid crystal display anda method for repairing defects thereof in which defects such as a shortcircuit between layers or a short circuit in a single layer that haveoccurred at steps for manufacturing the liquid crystal display areeasily recovered (repaired) to provide a good product with a probabilityhigher than that in the related art.

2. Description of the Related Art

FIG. 30 shows an example of a configuration of an active matrix liquidcrystal display. The liquid crystal panel has a structure in which twoglass substrates, i.e., a TFT substrate 200 formed with TFTs (thin filmtransistors) and the like and a CF substrate 204 formed with a colorfilter (CF) and the like are in a face-to-face relationship with eachother and are bonded together with liquid crystals 204 sealedtherebetween.

FIG. 31 shows an equivalent circuit of elements formed on the TFTsubstrate 200. A plurality of gate bus lines 218 extending horizontallyin FIG. 31 are formed on the TFT substrate 200, and a plurality of drainbus lines 220 extending vertically in FIG. 31 are formed in parallelwith each other in an intersecting relationship with the gate bus lines.Each of the regions enclosed by the plurality of gate bus lines 218 anddrain bus lines 220 serves as a pixel region. A TFT 222 and a displayelectrode 224 made of a transparent electrode material are formed in apixel region. Each TFT 222 is connected to an adjacent drain bus line220 at a drain electrode thereof, to an adjacent gate bus line 218 at agate electrode thereof and to a display electrode 224 at a sourceelectrode thereof. Storage capacitor bus lines 226 are formed on thesubstrate surface under the display electrodes 224 in parallel with thegate bus lines 218. The TFTs 222 and the bus lines 218, 220 and 226 areformed using a photolithographic step at which a series of semiconductorprocesses, i.e., film formation, resist application, exposure,development, etching and resist removal are repeated.

Referring again to FIG. 30, a gate driving circuit 206 loaded withdriver ICs for driving the plurality of gate bus lines 218 and a draindriving circuit 208 loaded with driver ICs for driving the plurality ofdrain bus lines 220 are provided on the TFT substrate 200 which isprovided in a face-to-face relationship with the CF substrate 204 withthe liquid crystals 204 sealed therebetween. Those driving circuits 206and 208 output scan signals and data signals to predetermined gate buslines 218 and drain bus lines 220 based on predetermined signals outputby a control circuit 216. A polarizer 212 is provided on the surface ofthe TFT 200 opposite to the surface thereof on which the elements areformed, and a back-light unit 214 is attached to the surface of thepolarizing plate 212 opposite to the TFT substrate 200. A polarizer 210in a crossed Nicol relationship with the polarizer 212 is attached tothe surface of the CF substrate 204 opposite to the surface thereof onwhich the color filter is formed.

The structure of the TFT 222 may be an inverted staggered type in whichsource and drain electrodes are formed above a gate electrode on asubstrate surface, a staggered type in which a gate electrode is formedabove source and drain electrodes, a planar type or the like. FIGS. 32a, 32 b and 32 c show a schematic configuration of a pixel region havinga typical inverted staggered type TFT. FIG. 32 a is an illustration ofthe pixel region obtained by viewing the substrate surface from above,and FIG. 32 b shows a section of the TFT taken along the line A-A inFIG. 32 a. FIG. 32 c shows a section of the region where the gate busline 218 (or storage capacitor bus line 226) intersects the drain busline taken along the line B-B in FIG. 32 a.

As shown in FIGS. 32 a, 32 b and 32 c, the TFT 222 is formed in thevicinity of the intersection between the gate bus line 218 and drain busline 220. A drain electrode 230 of the TFT 222 is formed by beingextended from the drain bus line 220. The edge portion of the drainelectrode 230 is located at one edge of an active semiconductor layer232 formed of amorphous silicon (a-Si) or polysilicon on the gate busline 218 and a channel protection film 242 formed thereon.

On the other hand, a source electrode 228 is formed at the other edge ofthe active semiconductor layer 232 and channel protection film 242. Insuch a configuration, the region of the gate bus line 218 directly underthe channel protection film 242 serves as a gate electrode of the TFT222.

As shown in FIG. 32 b, a gate insulation film 240 is formed on the gatebus line 218, and the active semiconductor layer 232 that constitutes achannel is formed on the gate insulation film 240 directly above thegate bus line 218. An auxiliary capacitor bus line 226 is also formedwhich horizontally extends substantially in the middle of the pixelregion. A storage capacitor electrode 236 for each pixel is formed abovethe auxiliary capacitor bus line 226 with the insulation film 240interposed therebetween. A pixel electrode 224 constituted by atransparent electrode is formed above the source electrode 228 andstorage capacitor electrode 236. The pixel electrode 224 is electricallyconnected to the source electrode 228 through a contact hole 234provided in a protective film 244 formed thereunder. The pixel electrode224 is also electrically connected to the storage capacitor electrode236 through a contact hole 238.

While the above-described TFT structure is of the inverted staggeredtype, for example, staggered type and planar type devices have aninverted structure in which a drain electrode is in the bottom layer anda gate electrode is located above the same. In any of those structures,what is to be noted is the fact that those metal layers are stacked inan intersecting relationship with each other with an insulation filminterposed therebetween.

FIGS. 33 a and 33 b show a conventional method for repairing ashort-circuit between metal layers caused by some reason. FIG. 33 a isan illustration of a pixel region obtained by viewing the substratesurface from above, and FIG. 33 b shows a section taken along the lineA-A in FIG. 33 a. FIG. 34 shows a repair line formed on a TFT substrate200. Components having the same functions and operations as those of thecomponents described with reference to FIGS. 30 through 32 c areindicated by like reference numbers and will not be described here.

FIGS. 33 a and 33 b show a state in which the storage capacitor bus line226 and drain bus line 220 penetrate through the gate insulation film240 to cause an inter-later short-circuit 290. The inter-layershort-circuit 290 causes a line defect because it hinders theapplication of a predetermined voltage to the drain bus line 220. Arepair is performed to repair the display defect using a laser.

According to this repairing method, first, the drain bus line 220 of thedefective pixel is irradiated with a laser beam to be cut in a cuttingposition 300 between the drain electrode 230 and inter-layershort-circuit 290. Second, the drain bus line 220 is irradiated with alaser beam to be cut in a cutting position 301 between the inter-layershort-circuit 290 and the drain electrode 230 of the next pixel. Thisisolates the shorting position of the inter-layer short-circuit 290.

Third, as shown in FIG. 34, spare lines (repair lines) 302 and 303provided in advance for a repair on the TFT substrate 200 are used toapply a predetermined voltage to the drain bus line 220 thus cut fromthe drain driving circuit 208.

A plurality of drain bus lines 220 formed in parallel at equal intervalsin a display area I shown in FIG. 34 converge at an extraction wiringportion II to be connected to a TCP (tape carrier package) which is anFPC (flexible printed circuit) loaded with driver ICs mounted using TAB(tape automated bonding) at a terminal portion III.

The repair line 302 is formed such that it intersects the plurality ofdrain bus lines 220 with the insulation film interposed at the end ofthe display area I on the side of the drain driving circuit 208 and isextended along with the plurality of drain bus lines 220 through theextraction wiring portion II to be connected to the TCP at the terminalportion III. The repair line 302 is formed of the same metal as used toform the gate bus lines 218 and is normally insulated from the drain buslines 220 by the insulation film 240.

When a defect attributable to an inter-layer short-circuit 290 occurs ata certain drain bus line 220, a region 304 where the drain bus line 220and the repair line 302 intersect with each other is irradiated with alaser beam to fuse those wiring metals together, which establishesconnection and conduction. Referring to conditions for the laserirradiation at such a repair, the laser must have intensity as shown inFIG. 1 d which will be described later.

The repair line 302 extends from the gate driving circuit 206 throughthe printed circuit board 250 to the repair line 303 on the unloadedside of the driving circuit. The repair line 303 on the unloaded side ofthe driving circuit is also formed of the same metal as used for theformation of the gate bus lines 218 and is formed such that itintersects the plurality of drain bus lines 220 with the insulation film240 interposed therebetween. During a repair, a region 304 where a drainbus line 220 having an inter-layer short-circuit 290 and the repair line302 intersect with each other is irradiated with a laser beam, and aregion 305 where the drain bus line 220 and the repair line 303intersect with each other is also irradiated with a laser beam to fuseboth of the lines, which establishes connection and conduction. Thus, apredetermined voltage is applied to the drain bus line 220 from whichthe shorting portion of the inter-layer short-circuit 290 has been cutoff also from the side opposite to the drain driving circuit 208 toperform a repair for preventing the occurrence of the line defect.

The number of the repair lines 302 and 303 determines the number ofdefects that can be relieved among a plurality of defects that haveoccurred in one panel. In view of demands for panels with smaller framesin these days, however, it is not preferable to increase the repairlines 302 and 303 because the area of the substrate occupied by therepair lines 302 and 303 is increased. Further, since an extra capacitoris generated at the regions where the repair lines 302 and 303 intersectthe drain bus lines 220, the drain driving circuit 208 has an increasedload, and this is another factor that discourages the increase of therepair lines. For example, even if two repair lines are provided in apanel, inter-later short-circuits at three or more drain bus linesdisable a complete repair, and this results in a defective panel. Repairlines are frequently required not only for inter-layer short-circuitsbut also for breakage of drain bus lines 220 and short-circuits in asingle layer, and those defects can render a panel defective when theyoccur in combination even if there is only one drain bus line that hasan inter-layer short-circuit.

A repair utilizing laser irradiation does not necessarily result insuccessful connection with a probability of 100%. The optimization oflaser conditions can only provides a probability in the range from 60 to80%, although it depends on the metal materials used. The probabilitycan only be improved up to about 90% even if the number of locations tobe irradiated with a laser beam is increased and, accordingly, defectivepanels are produced in a probability of 10%.

A repair of connection according to the related art utilizing laserirradiation involves irradiation of a multiplicity of locations in apanel with a laser beam even if there is an inter-layer short-circuit inonly one location, which has resulted in a problem in that the repairbecomes very much complicated and induces operational errors such asmisaddressing a location to be irradiated with a laser beam.

As described above, according to the related art, repair lines 302 and303 are provided on an assumption that a line breakage or the likeexists in a display area I as shown in FIG. 34. Recent demands forpanels with smaller frames have increased the possibility of defectssuch as breakage and shorting of a lines because such demands havenecessitated a smaller line width and a smaller line interval at anextraction wiring portion II. This has resulted in a need for arepairing method which can cope with defects at an extraction wiringportion II.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a display and a method forrepairing defects of the same in which defects such as an inter-layershort-circuit and a short-circuit in a single layer that have occurredat steps for manufacturing the display can be easily repaired to providea good product with a probability higher than that in the related art.

The above-described object is achieved by a method for repairing defectsof a display having pixel regions formed on a substrate, comprises thesteps of irradiating a multi-layer region formed by stacking a pluralityof conductive layers with insulation layers interposed with a laser beamand selectively removing only an upper conductive layer in the vicinityof the multi-layer region such that neither inter-layer short-circuitnor short-circuit in a single layer occurs in the multi-layer region.

The present invention makes it possible to repair an inter-layershort-circuit using no repair line. By optimizing the output power of alaser, it is possible to melt or vaporize only either of stacked metalsor to melt and vaporize both of them such that they are not fused andconnected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a through 1 e illustrate a method for repairing a defect in adisplay according to a first mode for carrying out the invention.

FIG. 2 illustrates the method for repairing a defect in a displayaccording to the first mode for carrying out the invention.

FIGS. 3 a and 3 b illustrate an example in which an inter-layershort-circuit is repaired by performing irradiation with a laser using arange IV according to the method for repairing a defect in a display inthe first mode for carrying out the invention.

FIGS. 4 a through 4 d illustrate an example in which an inter-layershort-circuit is repaired by performing irradiation with a laser using arange II according to the method for repairing a defect in a display inthe first mode for carrying out the invention.

FIGS. 5 a through 5 c illustrate an example in which an inter-layershort-circuit is repaired by performing irradiation with a laser using arange II according to the method for repairing a defect in a display inthe first mode for carrying out the invention.

FIGS. 6 a and 6 b illustrate a modification of the example of a repairof an inter-layer short-circuit by performing irradiation with a laserusing a range II according to the method for repairing a defect in adisplay in the first mode for carrying out the invention.

FIGS. 7 a through 7 d illustrate an example in which a short-circuit ina single layer is repaired by performing irradiation with a laser usinga range II according to the method for repairing a defect in a displayin the first mode for carrying out the invention.

FIG. 8 schematically illustrates a first embodiment of a method forrepairing a defect in a display in a second mode for carrying out theinvention.

FIG. 9 schematically illustrates a second embodiment of a method forrepairing a defect in a display in the second mode for carrying out theinvention.

FIG. 10 schematically illustrates a third embodiment of a method forrepairing a defect in a display in the second mode for carrying out theinvention.

FIG. 11 schematically illustrates a first embodiment of a method forrepairing a defect in a display in a third mode for carrying out theinvention.

FIG. 12 schematically illustrates the first embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIG. 13 schematically illustrates a modification of the first embodimentof a method for repairing a defect in a display in the third mode forcarrying out the invention.

FIG. 14 schematically illustrates another modification of the firstembodiment of a method for repairing a defect in a display in the thirdmode for carrying out the invention.

FIG. 15 schematically illustrates a second embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIG. 16 schematically illustrates a third embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIG. 17 schematically illustrates a fourth embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIG. 18 schematically illustrates a fifth embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIG. 19 schematically illustrates a sixth embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIG. 20 schematically illustrates a seventh embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIG. 21 schematically illustrates an eighth embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIG. 22 schematically illustrates the eighth embodiment of a method forrepairing a defect in a display in the third mode for carrying out theinvention.

FIGS. 23 a, 23 b, and 23 c schematically illustrate a first embodimentof a method for repairing a defect in a display in a fourth mode forcarrying out the invention.

FIGS. 24 a, 24 b and 24 c schematically illustrate a second embodimentof a method for repairing a defect in a display in the fourth mode forcarrying out the invention.

FIGS. 25 a and 25 b schematically illustrate a third embodiment of amethod for repairing a defect in a display in the fourth mode forcarrying out the invention.

FIGS. 26 a and 26 b schematically illustrate a fourth embodiment of amethod for repairing a defect in a display in the fourth mode forcarrying out the invention.

FIG. 27 schematically illustrates a fifth embodiment of a method forrepairing a defect in a display in the fourth mode for carrying out theinvention.

FIGS. 28 a and 28 b schematically illustrate a sixth embodiment of amethod for repairing a defect in a display in the fourth mode forcarrying out the invention.

FIGS. 29 a and 29 b schematically illustrate a seventh embodiment of amethod for repairing a defect in a display in the fourth mode forcarrying out the invention.

FIG. 30 illustrates a schematic configuration of a liquid crystaldisplay.

FIG. 31 illustrates a schematic configuration of an element portion of aliquid crystal display.

FIGS. 32 a, 32 b and 32 c illustrate a schematic configuration of anelement portion of a liquid crystal display.

FIGS. 33 a and 33 b illustrate a method for repairing a liquid crystaldisplay according to the related art.

FIG. 34 illustrates a method for repairing a liquid crystal displayaccording to the related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be made on a method for repairing a defect in adisplay according to a first mode for carrying out the invention withreference to FIGS. 1 a through 7 d. First, the method for repairing adefect according to the present mode for carrying out the invention willbe schematically described with reference to FIGS. 1 a through 2.Components having the same functions and operations of those accordingto the related art shown in FIGS. 30 through 33 b will be indicated bylike reference numbers and will not be described here.

FIGS. 1 a through 1 e show the relationship between the output intensityof a YAG laser used for a repair and states of two metal layersvertically stacked with an insulation film interposed therebetween. FIG.1 a is a graph whose abscissa axis represents the output intensity ofthe laser and whose ordinate axis represents the rate of connectionbetween the two metal layers. The output intensity of the laser isdivided into four stages or ranges I through IV based on the rate ofconnection between the two metal layers. FIGS. 1 b through 1 e aresectional views of the substrate showing states of the two metal regionsin the respective four stags or ranges I through IV of the outputintensity of the laser divided based on the graph of FIG. 1 a.

In the substrate to be repaired shown in FIGS. 1 b through 1 e, gate buslines 218 (or storage capacitor bus lines 226) are formed as a firstmetal layer (conductive layer) on a TFT substrate 200 constituted by a0.7 mm thick glass substrate, and a gate insulation film 240 is formedon the same. The first metal layer is formed by a 100 nm thick aluminum(Al) layer and a 50 nm thick titanium (Ti) layer stacked on the same.The gate insulation film 240 is constituted by a silicon nitride film(SiN) having a thickness of 350 nm.

Drain bus lines 220 as a second metal layer (conductive layer)intersecting the first metal layer are formed on the gate insulationfilm 240, and a protective film 244 is formed on the entire uppersurface of the substrate. The second metal layer is formed by a 20 nmthick Ti layer, a 75 nm thick Al layer and a 80 nm thick Ti layerstacked in the same order. The protective film 244 is constituted by SiNwith a thickness of 330 nm.

FIG. 1 b shows a state of the surface of the TFT substrate 200 whenirradiated with a laser beam E with low intensity within the range I inthe graph of FIG. 1 a. In the range I where the laser output is quiteweak, since the second metal layer that is the upper layer can not besufficiently melted, only a part of the upper layer of the second metallayer is vaporized and the second metal layer can not be cut andisolated.

FIG. 1 c shows a state of the surface of the TFT substrate 200 whenirradiated with a laser beam E within the range II having intensityslightly higher than that in the range I in the graph of FIG. 1 a. Inthe range II, only the second metal layer which is the upper layer canbe melted and vaporized to be cut and isolated. Since the irradiationenergy of the laser beam E is consumed only in breaking the second metallayer, it has no influence on the underlying gate insulation film 240and first metal layer (218, 226) whose state therefore undergoes nochange.

FIG. 1 d shows a state of the surface of the TFT substrate 200 whenirradiated with a laser beam E within the range III having intensityhigher than that in the range II in the graph of FIG. 1 a. In the rangeIII, not only the upper second metal layer but also the lower firstmetal layer is melted and vaporized, and those metals partially contactagain and mix each other. Therefore, the first and second metal layersare likely to be connected with each other.

FIG. 1 e shows a state of the surface of the TFT substrate 200 whenirradiated with a laser beam E within the range IV having intensityhigher than that in the range III in the graph of FIG. 1 a. In the rangeIV where the laser output is further enhanced, while both of the firstand second metal layers are melted and vaporized, the probability ofconnection between the first and second metal layers is decreasedbecause vaporization occurs at a higher rate because of the increasedirradiation energy.

The present mode for carrying out the invention is characterized in thata repair of a defect is carried out by means of laser irradiation usingthe range II or IV among the above-described ranges I through IV of theintensity of a laser beam. In practice, the laser output valuesignificantly varies depending on the metals to be irradiated and thematerial, quality, thickness and shape of the insulation film and,therefore, the laser output value can not be limited to any generalrange of numerical values. However, a normal laser repairing apparatusmay be used in such a range II or IV on a TFT substrate which is acombination of common materials. FIG. 2 is a graph whose ordinate axisrepresents the rate (%) of successful removal of only an upper metal ofa TFT substrate and whose abscissa axis represents the output (relativevalues) of the laser. According to an experiment in which a low laseroutput resulting in successful removal, i.e., successful cutting of theupper layer metal at a rate of 0% is represented by 100, laser outputswith relative values of 160, 205 and 250 result in rates of successfulremoval of 78%, 96% and 100%, respectively. When the laser output isfurther increased to relative values of 295, 340 and 440, the rate ofsuccessful removal decreases to 69.2%, 50% and 0%, respectively. Thisindicates that the range of the laser output with relative values lowerthan 160, the range with relative values higher than 295 and the rangewith relative values between 160 and 295 inclusive can be used as theranges I, III and II, respectively.

A description will now be made with reference to FIGS. 3 a and 3 b on anexample in which an inter-layer short-circuit is repaired by performingirradiation with a laser using the range IV. FIG. 3 a shows a state ofthe surface of the TFT substrate 200 in which there is an inter-layershort-circuit 290 substantially in the middle of an intersection betweena gate bus line 218 and a drain bus line 220. In this case, theinter-layer short-circuit 290 is irradiated with a laser beam havingoutput intensity within the range IV. In doing so, the laser beam isprojected through a slit S for limiting the beam within a region to beirradiated that encloses only the inter-layer short-circuit 290 in ordernot to break the drain bus line 220 and gate bus line 218. While thedrain bus line 220 and gate bus line 218 are connected when theintensity of the laser beam is low and is actually at the level of therange III, the connection can be broken with an increased probability byperforming irradiation again with the slit S adjusted to enlarge theirradiated region slightly. Further, the repair can be performedreliably and easily by repeating the irradiation with a laser beam untilthe resistance of the short-circuit sufficiently increases whilemeasuring the resistance using a tester or the like. FIG. 3 b shows astate realized after the inter-layer short-circuit 290 is repaired. Theinter-layer short-circuit 290 has been eliminated and replaced by a holehaving a configuration substantially the same as the slit S whichextends to the surface of the glass substrate, and no short-circuit hasoccurred between the drain bus line 220 and gate bus line 218.

A description will now be made with reference to FIGS. 4 a through 4 dand FIGS. 5 a through 5 c on an example in which an inter-layershort-circuit is repaired by performing irradiation with a laser usingthe range II. FIGS. 4 a through 4 d are sectional views of the TFTsubstrate 200 showing states in which a gate bus line 218 is formed onthe TFT substrate 200 and in which a drain bus line 220 intersects thesame with a gate insulation film 240 interposed therebetween. FIGS. 4 aand 4 b show proper laser irradiation using the range II according tothe present mode for carrying out the invention, and FIGS. 4 c and 4 dshow an example of improper laser irradiation which is not in accordancewith the present mode for carrying out the invention.

In FIG. 4 a, a region where the drain bus line 220 completely covers thegate bus line 218 is irradiated with a laser beam E having intensitywithin the range II. As shown in FIG. 4 b, this prevents the laser beamE from directly irradiating the gate bus line 218 and thus makes itpossible to melt and vaporize only the drain bus line 220.

In FIG. 4 c, both of the drain bus line 220 and gate bus line 218 areirradiated with the laser beam E having intensity within the range II.In this case, the gate bus line 218 is also irradiated with the laserbeam E and, therefore, not only the drain bus line 220 but also the gatebus line 218 is melted and vaporized. This can result in a short-circuitbetween the drain bus line 220 and gate bus line 218 as shown in FIG. 4d.

A description will now be made with reference to FIGS. 5 a through 5 con an example in which an inter-layer short-circuit is repaired byperforming irradiation with a laser using the range II. FIG. 5 a shows astate of the surface of the TFT substrate 200 in which there is aninter-layer short-circuit 290 in the vicinity of an edge of a drain busline 220 at an intersection between a gate bus line 218 and the drainbus line 220.

A laser beam irradiation apparatus for a repair according to the relatedart can irradiate an object by adjusting a slit S having a rectangularirradiating area to change the size of the irradiating area. Therefore,as described with reference to FIGS. 4 a through 4 d, laser irradiationhaving an output within the range II is carried out as a first cycle oflaser irradiation by forming a slit S1 in a region where the drain busline 220 completely covers the gate bus line 218. As a result of thislaser irradiation, a cut portion longer than the width of the gate busline 218 is formed adjacent to the inter-layer short-circuit 290 suchthat it splits the intersecting portion of the drain bus line 220 intotwo parts, as shown in FIG. 5 b. Next, as shown in FIG. 5 c, slits S2and S3 are respectively used for second and third cycles of laserirradiation with an output within the range II to cut the drain bus line220 at both ends of the cut portion (indicated by S1), thereby isolatingthe inter-layer short-circuit 290 of the drain bus line 220. The orderof laser irradiation may be the reverse of that described above.

As shown in FIGS. 6 a and 6 b, the use of a U-shaped slit (see S4 inFIG. 6 a), an arcuate slit (see S5 in FIG. 6 b) or the like will make itpossible to complete a repair of a defect in one cycle of laser beamirradiation.

A description will now be made with reference to FIGS. 7 a through 7 don examples in which a short-circuit in a single layer is repaired byperforming irradiation with a laser using the range II. FIG. 7 a shows astate of the surface of the TFT substrate 200 in which there is ashort-circuit 291 between two drain bus lines 220 in the same layer inthe vicinity of intersections between a gate bus line 218 and the drainbus lines 220. In the example shown in FIG. 7 a, the short-circuit 291in the same layer completely covers the gate bus line 218 in thevicinity of the region thereof connected to the drain bus line 220 onthe left side. Therefore, a slit S is focused on the same region, andlaser irradiation having an output within range II is performed with theshape of the slit S adjusted such that the short-circuit 291 in the samelayer is cut along the drain bus line 220. As shown in FIG. 7 b, thislaser irradiation makes it possible to break the short-circuit 291 inthe same layer in the region of a slit S6, thereby eliminating theshort-circuit between the two drain bus lines 220 without irradiatingthe gate bus line 218 in the underlying layer with a laser beam.

Similarly to FIG. 7 a, FIG. 7 c shows a state of the surface of the TFTsubstrate 200 in which there is a short-circuit 291 in a single layerbetween two drain bus lines 220 in the vicinity of intersections betweena gate bus line 218 and the drain bus lines 220. In the example shown inFIG. 7 c, however, the short-circuit 291 in the single layer has noregion which completely covers the gate bus line 218. In this case,similarly to the example described with reference to FIGS. 5 a through 5c, laser irradiation with an output within the range II is performed asa first cycle of laser irradiation by forming a slit S7 in a region onthe left drain bus line 220 which completely covers the gate bus line218. As a result of this laser irradiation, a cut portion S7 longer thanthe width of the gate bus line 218 is formed such that it splits theintersecting portion of the left drain bus line 220 into two parts, asshown in FIG. 7 b. Next, slits S8 and S9 are respectively used forsecond and third cycles of laser irradiation with an output within therange II to cut the drain bus line 220 at both ends of the cut portionS7. This makes it possible to isolate the short-circuit 291 in thesingle layer from the left drain bus line 220, thereby eliminating theshort-circuit between the two drain bus lines 220 without irradiatingthe gate bus line 218 in the underlying layer with a laser beam.Obviously, the order of laser irradiation may be the reverse of thatdescribed above.

The above-described repairing method in the present mode for carryingout the invention may be used in combination with a repairing methodaccording to the related art in which repair lines are formed on asubstrate. In this case, satisfactory effects can be achieved even ifthe present mode for carrying out the invention is not 100% successful.For example, when inter-layer short-circuits are present in threelocations of a panel formed with two repair lines to allow up to twolocations to be repaired, the repairing method in the present mode maybe used for the three locations and, if only one of the locations issuccessfully repaired, the remaining two locations can be repaired usingthe repairing method according to the related art in which the drain buslines 220 are cut and connected to the repair lines. Further, thepresent mode for carrying out the invention allows easier operations andinduces less errors compared to the conventional repairing method thatinvolves line connection because it only involves irradiation ofdefective parts with a laser beam. This makes it possible to repairdefects such as inter-layer short-circuits and short-circuits in asingle layer easily with a probability higher that in the related art.

A description will now be made with reference to FIGS. 8 through 10 on amethod for repairing a defect in a display according to a second modefor carrying out the invention. In the present mode for carrying out theinvention, a method for repairing a breakage in a gate bus line will bedescribed. Components having the same functions and operations as thosein the first mode for carrying out the invention will be indicated bylike reference numbers and will not be described.

The present mode for carrying out the invention is characterized in thata bypass for a broken portion 292 of a gate bus line 218 is formed byseparating or connecting it from or to a drain electrode 230 or a sourceelectrode 228 of a TFT or a pixel electrode 224 or a storage capacitorbus line 226 which is formed above the gate bus line 218 with aninsulation film 240 interposed through local irradiation with a laserbeam, thereby allowing the broken portion 292 of the gate bus line 218to be repaired.

The invention will now be described with reference to specificembodiments.

A first embodiment will now be described.

FIG. 8 shows a plurality of pixel regions as seen when the substratesurface is viewed from above, each of the pixels having the samestructure as that shown in FIGS. 32 a through 32 c. In FIG. 8, a gatebus line 218 a that horizontally extends substantially in the middle ofthe figure is broken at a broken portion 292.

First, a laser beam irradiates a cutting position 310 between a regionwhere a drain electrode 230 b and a drain bus line 220 b are connectedand an intersection between the drain bus line 220 b and the gate busline 218 a to cut the drain bus line 220 b. Then, a cutting position 312at the base of a drain electrode 230 a which extends from a drain busline 220 a to a position above the gate bus line 218 a is cut byirradiating the same with a laser beam. Then, a laser beam is scannedalong a storage capacitor bus line 226 a to irradiate a cutting position313 between the drain bus line 220 a and a pixel electrode 224 aadjacent thereto, a cutting position 314 between the drain bus line 220b and a pixel electrode 224 b adjacent thereto and a cutting position315 substantially in the middle of the storage capacitor bus line 226 abetween the cutting positions 313 and 314, which isolates a part of thestorage capacitor bus line along with the upper half of the pixelelectrode 224 a and a part of a storage capacitor electrode 236. As aresult, a first isolated line 221 is defined by the cutting positions310 and 315, and a second isolated line 227 is defined by the cuttingpositions 313, 314 and 315.

The cutting position 315 must be irradiated with a laser beam havingintensity controlled such that no inter-layer short-circuit occurs at anintersection between the storage capacitor bus line 226 a and drain busline 220 b. It is difficult to control the intensity of a laser beamirradiating a continuous linear configuration like the cutting position315, although it is relatively easy in the case of irradiation of aspot. Therefore, a short-circuit can occur between the storage capacitorbus line 226 a and drain bus line 220 b. When an inter-layershort-circuit occurs at an intersection between the storage capacitorbus line 226 a and drain bus line 220 b, a normal drain signal can notbe supplied even if the drain bus line 220 b beyond the first isolatedline 221 is relieved using a repair line similar to that in the relatedart. In order to prevent such a situation reliably, a cutting position311 located on the side of the cutting position 315 opposite to thefirst isolated line 221 is irradiated with a laser beam to ensure thedisconnection between the storage capacitor bus line 226 a and the drainbus line 220 b beyond the cutting position 315.

Next, two connecting positions 316 at an intersection between the firstisolated line 221 and gate bus line 218 a are irradiated with a laserbeam to short the first isolated line 221 and gate bus line 218 a at theintersection. Further, two connecting positions 317 of a sourceelectrode 228 a located in a face-to-face relationship with the drainelectrode 230 a whose base has been cut are irradiated with a laser beamto short the gate bus line 218 a and source electrode 228 a. Then, twoconnecting positions 318 of the second isolated line (including a partof the storage capacitor electrode 236) 227 are irradiated with a laserbeam to short the upper half of the pixel electrode 224 a and the secondisolated line 227. Further, a connecting position 319 is irradiated witha laser beam to short the second isolated line 227 and first isolatedline 221.

This establishes electrical connection between the source electrode 228a, pixel electrode 224 a, second isolated line 227 and first isolatedline 221. One end of the broken gate bus line 218 a is electricallyconnected to the source electrode 228 a, and the other end iselectrically connected to the first isolated line 221. Therefore, thegate bus line 218 a is capable of supplying a gate pulse to pixelregions other than the pixel region where the halved pixel electrode 224a is located. The drain bus line 220 b broken to form the first isolatedline 221 can be relieved using a repair line similar to that in therelated art to drive all pixels connected to the drain bus line 220 bproperly.

Thus, the present mode for carrying out the invention makes it possibleto repair a breakage in a gate bus line at the sacrifice of only onepixel in total.

A second embodiment will now be described.

FIG. 9 shows a plurality of pixel regions as seen when a substratesurface is viewed from above, each of the pixels having the samestructure as that shown in FIG. 8. In FIG. 9, a gate bus line 218 ahorizontally extending substantially in the middle of the figure isbroken at a broken portion 293 having a length which substantiallycorresponds to one pixel region.

First, a laser beam irradiates a cutting position 330 between aconnecting portion of a drain electrode 230 b on a drain bus line 220 band an intersection region between the drain bus line 220 b and the gatebus line 218 a to cut the drain bus line 220 b. Then, a cutting position332 which is closer to a drain driving circuit than a drain electrode230 a connected to a drain bus line 220 a is irradiated with a laserbeam to cut the drain bus line 220 a. Then, a laser beam is scannedalong a storage capacitor bus line 226 a to irradiate cutting positions334 and 335 which are located outside the drain bus lines 220 a and 220b respectively and which are not in contact with adjacent pixelelectrodes 224 and to irradiate a cutting position 336 substantially inthe middle of the storage capacitor bus line 226 a between the cuttingpositions 334 and 335. As a result, a first isolated line 350 isolatedfrom the drain bus line 220 a and a second isolated line 351 isolatedfrom the drain bus line 220 b are defined. Further, a part of thestorage capacitor bus line 226 a is isolated along with the upper halfof the pixel electrode 224 a and a part of a storage capacitor electrode236 to form a third isolated line 352.

In consideration to the possibility of an inter-layer short-circuit atan intersection between the storage capacitor bus line 226 a and drainbus line 220 a or an intersection between the storage capacitor bus line226 a and drain bus line 220 b, a cutting position 337 located on theside of the cutting position 336 opposite to the first isolated line 350is irradiated with a laser beam to ensure the disconnection between thestorage capacitor bus line 226 a and the drain bus line 220 a beyond thecutting position 337. Similarly, a cutting position 338 located on theside of the cutting position 336 opposite to the second isolated line351 is irradiated with a laser beam to ensure the disconnection betweenthe storage capacitor bus line 226 a and the drain bus line 220 b beyondthe cutting position 338.

Next, two connecting positions 320 at an intersection between the firstisolated line 350 and gate bus line 218 a are irradiated with a laserbeam to short the first isolated line 350 and gate bus line 218 a at theintersection. Further, two connecting portions 321 at an intersectionbetween the second isolated line 351 and gate bus line 218 a areirradiated with a laser beam to short the second isolated line 351 andgate bus line 218 a at the intersection.

Further, a connecting portion 322 is irradiated with a laser beam toshort the first isolated line 350 and third isolated line 352, and aconnecting portion 323 is irradiated with a laser beam to short thesecond isolated line 351 and third isolated line 352.

This establishes electrical connection between the first, second andthird isolated lines 350, 351 and 352. One end of the broken gate busline 218 a is electrically connected to the first isolated line 350, andthe other end is electrically connected to the second isolated line 351.Therefore, the gate bus line 218 a is capable of supplying a gate pulseto pixel regions other than the pixel region where the halved pixelelectrode 224 a is located. The drain bus line 220 b broken to form thesecond isolated line 351 can be relieved using a repair line similar tothat in the related art to drive all pixels connected to the drain busline 220 b properly.

Thus, the present mode for carrying out the invention makes it possibleto repair a breakage in a gate bus line at the sacrifice of only onepixel in total.

A third embodiment will now be described.

FIG. 10 shows a plurality of pixel regions as seen when the substratesurface is viewed from above, each of the pixel regions having the samestructure as that shown in FIG. 8. In FIG. 10, a gate bus line 218 ahorizontally extending substantially in the middle of the figure isbroken at a broken portion 293 under a drain bus line 220 b.

First, a cutting position 340 located closer to a drain driving circuitthan a drain electrode 230 b connected to the drain bus line 220 b isirradiated with a laser beam to cut the drain bus line 220 b. Then, acutting position 342 at the base of a drain electrode 230 a whichextends from a drain bus line 220 a to a position above the gate busline 218 a is irradiated with a laser beam to cut the same. Then, alaser beam is scanned along a storage capacitor bus line 226 a toirradiate a cutting position 344 between the drain bus line 220 a and apixel electrode 224 a adjacent thereto, a cutting position 345 betweenthe drain bus line 220 b and a pixel electrode 224 b adjacent theretoand a cutting position 346 substantially in the middle of the storagecapacitor bus line 226 a between the cutting positions 344 and 345. As aresult, a part of the storage capacitor bus line is isolated along withthe upper half of the pixel electrode 224 a and a part of a storagecapacitor electrode 236. As a result, a first isolated line 352 isdefined by the cutting positions 340 and 346, and a second isolated line354 is defined by the cutting positions 344, 345 and 346.

In consideration to the possibility of an inter-layer short-circuit atan intersection between the storage capacitor bus line 226 a and drainbus line 220 b, a cutting position 347 located on the side of thecutting position 346 opposite to the first isolated line 352 isirradiated with a laser beam to ensure the disconnection between thestorage capacitor bus line 226 a and the drain bus line 220 b beyond thecutting position 347.

Next, two connecting positions 324 between the drain electrode 230 b andgate bus line 218 a are irradiated with a laser beam to short the gatebus line 218 a, the drain electrode 230 b and the first isolated line352 connected thereto. Further, two connecting positions 325 between asource electrode 228 a located opposite to the drain electrode 230 awhose base portion has been cut and the gate bus line 218 a areirradiated with a laser beam to short the gate bus line 218 a and thesource electrode 228 a. Then, two connecting positions 326 of the secondisolated line (including a part of the storage capacitor electrode 236)354 are irradiated with a laser beam to short the upper half of thepixel electrode 224 a and the second isolated line 354. Further, aconnecting position 327 is irradiated with a laser beam to short thesecond isolated line 354 and first isolated line 352.

This establishes electrical connection between the source electrode 228a, pixel electrode 224 a, second isolated line 354 and first isolatedline 352. One end of the broken gate bus line 218 a is electricallyconnected to the source electrode 228 a, and the other end iselectrically connected to the drain electrode 230 b which is connectedto the first isolated line 352. Therefore, the gate bus line 218 a iscapable of supplying a gate pulse to pixel regions other than the pixelregion where the halved pixel electrode 224 a is located and the pixelregion with the drain electrode 230 b connected to the first isolatedline 352. The drain bus line 220 b broken to form the first isolatedline 352 can be relieved using a repair line similar to that in therelated art to properly drive pixels connected to the drain bus line 220b other than the pixel with the pixel electrode 224 b.

Thus, the present mode for carrying out the invention makes it possibleto repair a breakage in a gate bus line at the sacrifice of only twopixels in total.

A description will now be made with reference to FIGS. 11 through 22 ona display and a method for repairing a defect in the same according to athird mode for carrying out the invention. The present mode for carryingout the invention is related to a method for repairing a line breakageat an extraction wiring portion II for gate bus lines 218 or drain buslines 220 as shown in FIG. 34. In a display in which a plurality of buslines are formed in parallel in a display area, the present mode forcarrying out the invention is characterized in that there is providedrepair lines for repairing a line breakage that has occurred at anextraction wiring portion between the display area and an externalconnection terminal portion for the plurality of bus lines. The presentmode for carrying out the invention will be described below withreference to embodiments. Components having the same functions as thosein the first and second modes for carrying out the invention will beindicated by like reference numbers and will not be described.

A first embodiment will now be described.

FIG. 11 illustrates a part of an extraction wiring portion II for drainbus lines 220 formed on a TFT substrate 200 and the neighborhood of thepart. FIG. 12 is a sectional view taken along the line A-A in FIG. 11.As shown in FIG. 11, a plurality of drain bus lines 220 formed inparallel in a display area I are bent at an angle at an extractionwiring portion II and are connected to respective external connectionterminals 402 at a terminal portion III. A repair line 400 is providedbetween a display area I in the vicinity of the extraction wiringportion II and the terminal portion III such that they encompass theregion of the extraction wiring portion II. The repair line 400 includestwo lines which intersect a plurality of drain bus lines 220 on bothsides of the display area I and terminal portion III when viewed fromthe surface of the TFT substrate 200. Those two lines are connected toeach other at an end of the extraction wiring portion II.

As shown in FIG. 12, the repair line 400 is formed from a metal that isused to form gate bus lines at the same time when the gate bus lines 218are formed on the TFT substrate 200. The repair line 400 forms amulti-layer structure in combination with the drain bus lines 220 with agate insulation film 240 interposed between them, and it is electricallyinsulated from the plurality of drain bus lines 220.

For example, when there is a breakage 404 in a certain drain bus line220 at an extraction wiring portion II as shown in FIG. 11, regions 406and 408 where the drain bus line 220 intersects the repair line 400 areirradiated with a laser beam to fuse the drain bus line 220 and repairline 400 together, thereby shorting them. Thus, a breakage in a drainbus line 220 at the extraction wiring portion II can be easily repaired.

FIG. 13 illustrates a modification of the present embodiment. Inaddition to repair lines 302 and 303 according to the related art asshown in FIG. 34, repair lines 410 which intersect the drain bus lines220 with an insulation film interposed therebetween are formed in thevicinity of a terminal portion III. The repair lines 410 are connectedto the repair lines 302 and 303. In such a configuration, a breakage ina drain bus line 220 at the display area I can be repaired byirradiating intersecting regions 304 and 305 (or 306 and 305) with alaser beam as in the related art, and a breakage of a drain bus line 220at the extraction wiring portion II can be repaired by irradiating theintersecting regions 304 and 306 with a laser beam as in the presentembodiment. This configuration can be quite easily implemented becauseit is required only to add the repair lines 410 to a panel according tothe related art.

A description will now be made with reference to FIG. 14 on a repair ofa short-circuit 412 in a single layer between adjoining drain bus lines220 utilizing a repair line 400 according to the present embodiment. Asshown in FIG. 14, when a short-circuit 412 in a single layer occurs at alocation where a sealing material 418 is applied to put two substratestogether, the sealing material 418 hinders the short-circuit 412 in thesingle layer from being cut as a result of direct irradiation with alaser beam. In this case, one of the drain bus lines 220 is cut at thecutting positions 414 and 416 which can be irradiated by a laser beam.Then, regions 406 and 408 where the drain bus line 220 intersects therepair line 400 are irradiated with a laser beam to fuse the drain busline 220 and repair line 400 together, thereby shorting them. Thus, ashort-circuit in a single layer between the drain bus lines 220 at theextraction wiring portion II can be easily repaired.

A second embodiment will now be described.

As shown in FIG. 15, the present embodiment is characterized in thatdefects at two locations in the extraction wiring portion II can behandled by providing a further repair line 420 outside the repair line400 and by irradiating intersecting regions 422 and 424 with a laserbeam to relieve the two drain bus lines 220. By providing a plurality ofrepair lines at the extraction wiring portion II, a plurality of defectsin the extraction wiring portion II can be relieved.

A third embodiment will now be described.

As shown in FIG. 16, the present embodiment is characterized in thatthree electrically insulated repair lines 400 are formed. That is, arepair line 400 a is formed in the display area I in the vicinity of theextraction wiring portion II, and a repair line 400 b is formed at theterminal portion III. The repair lines 400 a and 400 b are formed at thesame time when the gate bus lines 218 are formed. A repair line 400 c isformed at the extraction wiring portion II such that it intersect therepair lines 400 a and 400 b with an insulation film interposedtherebetween.

For example, when there is a breakage 404 in a certain drain bus line220 at the extraction wiring portion II as shown in FIG. 16, regions 408and 406 where the drain bus line 220 intersects the repair lines 400 aand 400 b respectively are irradiated with a laser beam to fuse thedrain bus line 220 and repair lines 400 a and 400 b together, therebyshorting them. At the same time, regions 428 and 426 where the repairline 400 c intersects the repair lines 400 a and 400 b respectively areirradiated with a laser beam to fuse the repair lines 400 c with therepair lines 400 a and 400 b, thereby shorting them.

This reduces the length of the repair line intersecting the drain busline 220 and allows capacitance applied to the drain bus line 220 to bedecreased when no repair is performed. As a result, the drain drivingcircuit 208 may have a smaller driving capacitance.

A fourth embodiment will now be described.

As shown in FIG. 17, the present embodiment is characterized in thatdefects in two locations of the extraction wiring portion II can behandled by providing repair lines 420 (420 a, 420 b, 420 c) having thesame configuration as the repair lines 400 (400 a, 400 b, 400 c) outsidethe repair lines 400 and by irradiating intersecting regions 422, 424and intersecting regions 430 and 434 with a laser beam to relieve thetwo drain bus lines 220. By providing a plurality of repair lines at theextraction wiring portion II, a plurality of defects in the extractionwiring portion II can be relieved.

A fifth embodiment will now be described.

FIG. 18 is a schematic view of an area around the extraction wiringportion II which corresponds to FIG. 13. The plurality of drain buslines 220 are divided into several blocks, and repair lines 400α, 400β,. . . are configured for respective blocks. The repair lines areinsulated between the blocks. This makes it possible to relieve a linebreakage at the extraction wiring portion II on a block basis.

A sixth embodiment will now be described.

FIG. 19 is a schematic view of an area around the extraction wiringportion II which corresponds to FIG. 13. The present embodiment ischaracterized in that a repair line 400 in the form of a ring isprovided such that it intersects all of the drain bus lines 220 unlikethe fifth embodiment. This makes it possible to relieve two broken lines440 and 442 at the extraction wiring portion II wherever in the singlering they occurs. In this case, intersecting regions 304, 306, 436 and438 are irradiated with a laser beam to connect the drain bus lines 220and the repair line 400; the ring formed by the repair line 400 is cutat cutting positions 444 and 446 inside the intersecting regions 304 and436 in the vicinity thereof; and the ring formed by the repair line 400is cut at cutting positions 448 and 450 inside the intersecting regions306 and 438 in the vicinity thereof. While the repair lines 400α, 400β,. . . of the fifth embodiment makes it possible to relieve only one linein each block, the present embodiment relieves a broken line with anincreased degree of freedom because the defect can be relieved whereverit occurs within the ring. Further, since redundant wiring can be cutoff in the vicinity of the intersecting regions 304, 306, 436 and 438,resistance and capacitance attributable to repair lines can be reduced.

A seventh embodiment will now be described.

As shown in FIG. 20, the present embodiment is characterized in that arepair line 400 is connected through a connection line 452 to a shortring 454 provided to prevent electrostatic faults. This prevents theoccurrence of a short-circuit attributable to electrostatic breakdown atan intersection between a drain bus line 220 and the repair line 400even if static electricity is generated at array processing for formingelements on a TFT substrate 200. Since the short ring 454 is cut at ascribe line 456 to be removed when the panel is completed, the drain busline 220 and repair line 400 are electrically isolated from each other.

An eighth embodiment will now be described.

FIG. 21 shows a part of an extraction wiring portion II for gate busline 218 formed on a TFT substrate 200 and the neighborhood of the same.FIG. 22 is a sectional view taken along the line A-A in FIG. 21. Asshown in FIG. 21, a plurality of gate bus lines 218 formed in parallelin a display area I are bent at an angle at an extraction wiring portionII and are connected to respective connection terminals 462 at aterminal portion III. A repair line 460 is provided between the displayarea in the vicinity of the extraction wiring portion II and theterminal portion III.

The repair line 460 includes two lines intersecting the gate bus lines218 on both sides of the display area I and terminal portion III asviewed from the surface of the TFT substrate 200, and those two linesare connected at the extraction wiring portion II. As shown in FIG. 22,the repair line 460 is in a multi-layer structure in which they areformed on the gate bus lines 218 on the TFT substrate 200 that is aglass substrate with gate insulation films 240 interposed therebetweenand is electrically insulated from the drain bus lines 218. The repairline 460 is formed from the metal used to form drain bus lines 220 atthe same time when the drain bus lines 220 are formed.

For example, when there is a breakage 464 in a certain gate bus line 218at the extraction wiring portion II as shown in FIG. 21, intersectingregions 466 and 468 between the gate bus line 218 and the repair line460 are irradiated with a laser beam to fuse the gate bus line 218 andrepair line 460 together, thereby shorting them. Thus, a breakage in agate bus line 218 at the extraction wiring portion II can be easilyrepaired.

As described above, the present mode for carrying out the inventionmakes it possible to a breakage in an extraction wiring portion, therebyallowing panels to be manufactured with improved yield. Further, therepair line which is newly provided does not increase the number ofmanufacturing steps because it is formed at the same step for formingdrain bus lines 220 or gate bus lines 218.

A description will now be made with reference to FIGS. 23 a through 29 bon a display in a fourth mode for carrying out the invention and amethod for repairing a defect in the same. In the present mode forcarrying out the invention, a description will be made on a defectrepairing method which is adapted to a breakage, short-circuit or thelike in a line and an extraction wiring portion. Recently, liquidcrystal panels are widely used as display devices of personal computersand personal digital assistants. There are increasing demands for costreduction in the market, and improved yield is an urgent requirement inthe field of manufacture. While a single or plurality of metal layershave been used for wiring at an extraction wiring portion II extendingfrom a terminal portion III to a display region I as shown in FIG. 34illustrating the related art, a line breakage can be caused by foreignsubstances entering at film forming steps to reduce the yield. Therecent trend toward larger screens with higher fidelity has increasedfine patterns in each of the bus lines, which has not only resulted inan increase in the probability of defects but also resulted in asituation in which even a redundant configuration encounters adifficulty in that a difference in line resistances during drivingappears as a line defect.

The present mode for carrying out the invention is characterized in thatauxiliary conductive thin film patterns in a partially or totallyoverlapping relationship with each other are formed as a wiringstructure for an extraction wiring portion II that extends from aterminal portion III to a display area I of an LCD panel. The auxiliaryconductive thin film patterns are electrically independent from eachother or are electrically connected to each other through a contact holeat one end thereof. In a case of a breakage defect in the middle of thewiring at the extraction wiring portion II extending from the terminalportion III to the display area I, the detective line is irradiated witha laser beam to be connected to the auxiliary conductive thin filmpatterns, which makes it possible to relieve the line with asubstantially negligible small difference in resistance from the othernormal bus lines, thereby improving the manufacturing yield of liquidcrystal panels.

The present mode for carrying out the invention will be described withreference to embodiments. In the present mode for carrying out theinvention, components having the same functions and operations as thosein the first, second and third modes for carrying out the invention willbe indicated by like reference numbers and will not be described.

A first embodiment will now be described.

FIG. 23 a shows a part of an extraction wiring portion II for drain buslines 220 formed on a TFT substrate 200 and the neighborhood of thesame. FIG. 23 b is a sectional view taken along the line A-A in FIG. 23a. As shown in FIGS. 23 a, 23 b and 23 c, a plurality of drain bus lines220 (FIG. 23 a shows only one of them) formed in parallel in a displayarea I are bent at an angle at an extraction wiring portion II and areconnected to respective external connection terminals 402 at a terminalportion III.

At the external connection terminal 402 for a drain bus line 220, thedrain bus line 220 which is a second metal layer is extended to aposition immediately before the terminal and is connected and switchedto a pad 606 which is a first metal layer through contact holes 600 and602 in an ITO film 604. The drain bus line 220 is wired and routed onlyin the second metal layer, and the first metal layer does not interferethe same. It is therefore possible to form the first metal layer asauxiliary line 500 under the drain bus lines 220 which is the secondmetal layer.

As shown in FIG. 23 b, the auxiliary line 500 is formed from the samemetal as that used to form the gate bus lines on the TFT substrate 200which is a glass substrate at the same time when the gate bus lines 218are formed. The auxiliary line 500 forms a multi-layer structure incombination with the drain bus liens 220 with a gate insulation filminterposed therebetween, and it is electrically insulated from the drainbus lines 220 and is in an electrically floating state in which it doesnot work as it is.

In the present embodiment, the auxiliary line 500 is formed under all ofthe drain bus lines 220 at the extraction wiring portion II. As shown inFIG. 23 c, when a drain bus line 220 is broken due to a foreignsubstance that has stuck thereto during a film forming step or aphotolithographic step, there has been no way other than discarding thepanel as defective according to the related art. In the presentembodiment, however, since the auxiliary line 500 is provided under thesame, the two positions 504 for laser irradiation on both sides of abroken position 502 of the broken drain bus line 220 are irradiated witha laser beam to fuse the drain bus line 220 and the auxiliary line 500together, thereby shorting them. Thus, a breakage in a drain bus line220 at the extraction wiring portion II can be easily repaired.

The above-described configuration and method for repairing a defect canbe equally applied to an extraction wiring portion II for gate bus lines218. In this case, the gate bus lines 218 correspond to the first metallayer, and the auxiliary line 500 corresponds to the second metal layer.

A second embodiment will now be described.

FIG. 24 a shows a part of an extraction wiring portion II for drain buslines 220 formed on a TFT substrate 200 and the neighborhood of thesame. FIG. 24 b is a sectional view taken along the line B-B in FIG. 24a. While the structure shown in FIGS. 24 a, 24 b and 24 c has the samebasic configuration as that shown in FIGS. 23 a, 23 b and 23 c, it ischaracterized in that one end of an auxiliary line 500 is connected todrain bus lines 220 in advance. Specifically, as shown in FIGS. 24 a and24 b, at an external connection terminal 402 for a drain bus line 220,the drain bus line 220 which is a second metal layer is extended to aposition immediately before the terminal and is connected throughcontact holes 600 and 602 in an ITO film 604 to a pad 606 which is afirst metal layer. One end of the auxiliary line 500 is connected to thepad 606.

Therefore, while the broken portion 502 must be irradiated with a laserbeam on both sides thereof in the configuration shown in FIGS. 23 a, 23b and 23 c, a broken line can be relieved by irradiating only oneposition 504 for laser irradiation on the side of the display area witha laser beam to establish connection. This makes it possible to reducethe number of steps for a repair operation significantly. Sinceconnection is established only at a broken portion, it is possible tosuppress the difference in resistance from a normal bus line. Whilecontact between a drain bus line 220 and the auxiliary line 500 isestablished on the side of the terminal portion III in the presentembodiment, the contact may be established at the end of the line on theside of the display area I.

A third embodiment will now be described.

FIG. 25 a shows a part of an extraction wiring portion II for drain buslines 220 formed on a TFT substrate 200 and the neighborhood of thesame. FIG. 25 b is a sectional view taken along the line A-A in FIG. 25a. The present embodiment relates to an improvement in operabilityduring irradiation with a laser, and the configuration of the embodimentitself is the same as that shown in FIGS. 24 a, 24 b and 24 c. When anend of the auxiliary line 500 is irradiated with a laser, there is apossibility that the auxiliary line 500 itself may be erroneously cutbecause the auxiliary line 500 has a small width. In the presentembodiment, a part of a line to be irradiated with a laser is expandedto provide a pad 608, which eliminates the possibility of cutting of theline itself to improve operability during a repair. The purpose ofproviding the pad 608 instead of making the entire line thicker is tominimize the possibility of the occurrence of a short-circuit betweenthe line and any pattern adjacent thereto and to avoid any increase ofthe load attributable to parasitic capacitance between the bus lines anda common electrode.

A fourth embodiment will now be described.

FIG. 26 a shows a part of an extraction wiring portion II for drain buslines 220 formed on a TFT substrate 200 and the neighborhood of thesame. FIG. 26 b is a sectional view taken along the line B-B in FIG. 26a. The present embodiment relates to an improvement of operabilityduring irradiation with a laser, and the configuration of the embodimentitself is the same as that shown in FIGS. 24 a, 24 b and 24 c. Thepresent embodiment is characterized in that lines in the first metallayer closer to the TFT substrate 200 which is a glass substrate areformed with a width X somewhat smaller than the Y of lines in the secondmetal layer.

When a breakage defect of a line at a terminal is repaired after thepanel is completed, the bottom surface of the TFT substrate 200 on whicha TFT array is provided is irradiated generally with a laser beam from arepairing laser 610 as shown in FIG. 26 b. This is because laserirradiation of the side of the substrate has a problem in that the fieldof the laser can be blocked by a BM (black matrix) and in that theintensity of the laser beam is likely to be decreased by obstacles suchas liquid crystals.

At this time, while an end of the line is irradiated with the laser inorder to prevent the line from being broken by mistake, repairingaccuracy can be deduced when the width X of auxiliary line 500constituted by the first metal layer is greater than the width Y ofdrain bus lines 220 constituted by the second metal layer because theposition irradiated by the laser beam can not be visually confirmed.Although it is convenient if the auxiliary line 500 and the drain buslines 220 have the same width, it is difficult to implement because ofthe problem of residual metals after etching. The rate of successfulconnection during a repair can be improved by forming the lines in thefirst metal layer with a width X somewhat smaller than the width Y ofthe lines in the second metal layer.

A fifth embodiment will now be described.

As shown in FIG. 27, the present embodiment is characterized in thatdrain bus lines 220 and auxiliary line 500 are connected throughconnecting lines 452 and 453 to short rings 454 and 455 provided toprevent electrostatic faults. It is empirically known that anelectrically floating pattern is vulnerable to electrostatic breakdownduring processing, and the breakage of such a pattern can be preventedby connecting the same to a short ring to release locally generatedelectrical charges. Even when static electricity is generated duringarray processing for forming elements on a TFT substrate 200, such anarrangement makes it possible to prevent a short-circuit attributable toelectrostatic breakdown from occurring at an intersection between adrain bus line 220 and the auxiliary line 500. When the panel iscomplete, since the short rings 454 and 455 are cut at a scribe line 456to be removed, the drain bus line 220 and the auxiliary line 500 areelectrically isolated.

A sixth embodiment will now be described.

FIGS. 28 a and 28 b show a configuration which is a combination of theabove-described first through fifth embodiments in the present mode forcarrying out the invention. FIG. 28 a shows an area around an extractionwiring portion for drain bus lines 220. FIG. 28 b shows an area aroundan extraction wiring portion for gate bus lines 218.

Terminals for the drain bus lines 220 and gate bus lines 218 havedifferent structures because those lines are provided in separate layersunless they are relocated. Although the terminals shown in FIGS. 28 aand 28 b have different routings, since redundant wiring is provided,the terminals for the drain bus lines 220 and gate bus lines 218 havesubstantially the same structure except for the layer configuration ofthe auxiliary line 500. This structure is advantageous not only in thata redundant structure to cope with a line breakage can be provided forboth of the drain bus lines 220 and gate bus lines 218 but also in thatsubstantially the same design rules can be used for the terminals.

A seventh embodiment will now be described.

The description of the present embodiment will refer to a more specificstructure with reference to FIGS. 29 a and 29 b. FIG. 29 a shows anextraction wiring portion II for drain bus lines 220 formed on a TFTsubstrate 200 and the neighborhood of the same. FIG. 29 b is a sectionalview taken along the line A-A in FIG. 29 a.

Referring to the materials for the bus lines in the present embodiment,gate bus lines 218 are formed of Al/MoN/Mo, and drain bus lines 220 areformed of MoN/Al/MoN/Mo. Both of those lines have a thickness of 200 nmthat contributes to resistance if their thickness is considered in termsof the thickness of the Al film having a low resistance as a conductoras a reference, and both of them have a sheet resistance of about 0.2Ω/□. Therefore, those lines have the same resistance if they have thesame width. For example, in the case of a 21-inch LCD panel of the SXGAclass (1280×1024 lines), since the line width is about 20 μm, theresistance of the same including the display area is on the order of 15KΩ. While the auxiliary line 500 has a similar sheet resistance, such aresistance causes no fluctuation of the resistance of normal linesbecause the auxiliary line 500 does not contribute to electricalconduction.

Connection established by means of irradiation with a laser beamsresults in a contact resistance on the order of 0.2 Ω which is anegligible magnitude when the resistance of the panel as a whole isconsidered. Referring to effects of fluctuations of such resistances ondisplay, it has been empirically confirmed that a line resistancedistribution of 5% or less does not appear as a line defect on a panelas described above. In the case of a breakage defect in a part of a busline, the bus line has a resistance with an infinite magnitude becauseit is broken. In this case, a laser-based repair operation is performedto connect the auxiliary line 500 such that the broken part can bebypassed. Even if this results in a change in the distance from theterminal portion of the bus line to the portion connected as a result ofthe laser-based repair, no change occurs in the line resistance becausethose lines have the same resistance.

Therefore, even when replacement is performed at a line breakagerepairing operation, substantially no change occurs in the voltage dropthat a pixel signal on the line undergoes before it reaches the displayarea because the replaced line and the properly operating part havingsubstantially the same resistance. Thus, a line which has been connectedusing a laser will not appear as a defect. Further, the same effect canbe expected also when wiring materials having different resistances areused by limiting the resistance difference to a small value through theadjustment of the thicknesses and widths of the lines.

As described above, the present mode for carrying out the inventionmakes it possible to relieve a line breakage defect at an extractionwiring portion extending from a terminal portion to a display area of aliquid crystal panel without any significant process change, therebyimproving manufactrung yield.

Specifically, when a breakage is caused in a bus line pattern by aforeign substance or the like that has stuck thereto, the panel isnormally discarded as a defective. With the present configuration,however, the function of the line can be recovered by connecting a metalline in another layer using a laser. Further, since the presentconfiguration is not affected by the number of line breakage defects, aplurality of line breakage defects can be repaired to relieve adefective panel.

The auxiliary line 500 has no influence on normal bus lines, and only abroken bus line is connected through irradiation with a laser.Therefore, only one route is formed as the current path of the line.Thus, there is substantially no difference in resistance between therepaired portion and properly working portion of the bus line, and nolight line defect appears by the resistance difference. Further, arepair operation involves only a small number of steps becauseconnection using a laser is required at only one connecting portion forone broken line.

Boundaries between lines can be visually recognized by forming the lowermetal layer smaller than the upper metal layer, which is advantageous inthat a repair operation is facilitated and in that a repair can beperformed in the middle of a line. By providing an original wiringpattern and a wiring pattern for repair with substantially the sameresistance, the difference in resistance between bus lines during arepair can be limited to a small value, which increases the margin ofdisplay quality.

Further, when the auxiliary line 500 which is a wiring pattern forrepair is formed as an independent pattern, while the pattern becomesmore vulnerable to a breakage due to static electricity at manufacturingsteps, the occurrence of a defect as a result of the provision of thispattern can be advantageously avoided by connecting it to a commonconnection pattern (short ring) which is provided on a mother glassoutside the panel through a terminal to protect the bus line wiring andthe auxiliary line 500 from electrostatic breakdown during processing ofthe panel.

The present invention is not limited to the above-described modes forcarrying out the same, and various modifications may be made.

For example, while the above-described modes for carrying out theinvention have been described with reference to an active matrix liquidcrystal display utilizing TFTs as switching elements as an example, thepresent invention is not limited thereto and may be applied to variousother displays such as active matrix liquid crystal displays utilizingnon-linear elements such as diode elements (MIM), passive type liquidcrystal displays, EL (electro-luminescence) displays and PDPs (plasmadisplays) and methods for repairing defects in them.

As described above, the present invention makes it possible to provide adisplay and a defect repairing method in which defects such asinter-layer short-circuits and short-circuits in a single layer thathave occurred at steps for manufacturing the display can be easilyrepaired with high probability to provide a good product.

1. A method for repairing a defect in a display having pixel regionsformed on a substrate, comprising the step of: irradiating a multi-layerregion, formed by stacking a plurality of conductive layers with aninsulation layer interposed between each of the conductive layers, witha laser beam to selectively remove only an upper conductive layer ofsaid multi-layer region, without removing any portions of the conductivelayer, or layers, located below the portion of the upper conductivelayer being removed, such that neither inter-layer short-circuit norshort-circuit in a single layer occurs in said multi-layer region.
 2. Amethod for repairing a defect in a display having pixel regions formedon a substrate, comprising the step of: irradiating a multi-layer regionformed by stacking a plurality of conductive layers with insulationlayers interposed therebetween, with a laser beam to remove saidplurality of conductive layers, stacked above each other, in saidmulti-layer region such that no inter-layer short-circuit occurs.
 3. Amethod for repairing a defect in a display having pixel regions formedon a substrate, comprising the step of: forming a bypass for a brokenportion of a gate bus line making an electrical path through at leasttwo of the following: a drain electrode, or a source electrode of a TFT,a pixel electrode, and a storage capacitor bus line, which is formedwith an insulation film interposed therebetween, said bypass beingformed through local irradiation with a laser beam, thereby allowingsaid broken portion to be repaired by sacrificing regular use of anassociated pixel.
 4. A display having a plurality of bus lines formed ina display area, comprising: said plurality of bus lines each beingdefined by three segments, a display area segment, an extraction wiringportion segment, and a terminal portion segment, where said extractionwiring portion segment is positioned between said display area segmentand said terminal portion segment; and a repair line connectable to aplurality of extraction lines, at said display area segments and saidterminal portion segments, but not at said extraction wiring portionsegments, said repair line being configured for repairing a linebreakage that has occurred in at least one of said extraction wiringportion segments.
 5. A display having a plurality of bus lines formed ina display area, comprising: an auxiliary line formed along said bus linein an extraction wiring portion via an insulation film for repairing aline breakage that has occurred at the extraction wiring portion;wherein said auxiliary line and said bus line each include a widenedportion, wherein said widened portions are stacked to form a pad that issituated at an intermediate portion of said bus line.
 6. A method forrepairing a defect in a display having pixel regions formed on asubstrate, comprising the step of: forming a bypass for a broken portionof a gate bus line by forming an alternate conductive path through apixel electrode and a source electrode, whereby regular use of anassociated pixel is sacrificed.
 7. The method according to claim 6,further comprising the steps of: creating a first electrically isolatedline on a portion of a storage capacitor bus line, wherein said storagecapacitor bus line is adjacent to said gate bus line, and furtherwherein said storage capacitor bus line is separated from said gate busline by said pixel being sacrificed; creating a second electricallyisolated line on a portion of a drain bus line; and forming said bypassby using local irradiation with a laser beam, said bypass consisting ofa conductive path that includes a first edge of said broken gate busline, said source electrode, said pixel being sacrificed, said firstelectrically isolated line, said second electrically isolated line, anda second edge of said broken gate bus line.
 8. The method according toclaim 7, wherein said conductive path also includes a drain electrodethat is positioned adjacent said second edge of said broken gate busline.
 9. A method for repairing a defect in a display having pixelregions, comprising the step of: forming a bypass for a broken portionof a gate bus line by forming an alternate conductive path around apixel electrode, whereby regular use of an associated pixel issacrificed.
 10. The method according to claim 9, further comprising thesteps of: creating a first electrically isolated line on a portion of afirst drain bus line that is adjacent to said pixel being sacrificed;creating a second electrically isolated line on a portion of a storagecapacitor bus line, wherein said storage capacitor bus line is adjacentto said gate bus line, and further wherein said storage capacitor busline is separated from said gate bus line by said pixel beingsacrificed; creating a third electrically isolated line on a portion ofa second drain bus line that is both adjacent to said pixel beingsacrificed and located on an opposite side of said pixel beingsacrificed than said first drain bus line; and forming said bypass byusing local irradiation with a laser beam, said bypass consisting aconductive path that includes a first edge of said broken gate bus line,said first electrically isolated line, said second electrically isolatedline, said third electrically isolated line and a second edge of saidbroken gate bus line.
 11. The method according to claim 10, furthercomprising the steps of: irradiating with a laser beam to form anadditional cut on said first drain bus line to ensure isolation of firstelectrically isolated line; and irradiating with a laser beam to form asecond additional cut on said second drain bus line to ensure isolationof said third electrically isolated line.
 12. A display having aplurality of bus lines formed in a display area, comprising: anauxiliary line, formed along said bus line in an extraction wiringportion via an insulation film, for repairing a line breakage that hasoccurred at the extension wiring portion; wherein a terminal end portionof said auxiliary line is electrically connected to a terminal endportion of bus line via contact holes, whereby repair of a brokenportion of said bus line may be accomplished by using laser irradiationto make only a single additional electrical connection between saidauxiliary line and said bus line.
 13. A method for repairing a defect ina display having pixel regions formed on a substrate, comprising thestep of: forming a bypass for a broken portion of a gate bus line bymaking a conductive path that electrically connects said gate bus lineto a source electrode of a TFT and a pixel electrode through localirradiation with a laser beam, thereby allowing said broken portion tobe repaired by sacrificing regular use of an associated pixel.
 14. Amethod for repairing a defect in a display having pixel regions formedon a substrate, comprising the step of: forming a bypass for a brokenportion of a gate bus line by making a conductive path that electricallyconnects said gate bus line to a pixel electrode and a drain bus linethrough local irradiation with a laser beam, thereby allowing saidbroken portion to be repaired by sacrificing regular use of anassociated pixel.